implemented amplitude metrics (#1141)

server/routes/metrics.js

@@ -0,0 +1,23 @@
+const { sendBatch, clientEvent } = require('../amplitude');
+
+module.exports = async function(req, res) {
+  try {
+    const data = req.body;
+    const deltaT = Date.now() - data.now;
+    const events = data.events.map(e =>
+      clientEvent(
+        e,
+        req.ua,
+        data.lang,
+        data.session_id + deltaT,
+        deltaT,
+        data.platform,
+        req.ip
+      )
+    );
+    const status = await sendBatch(events);
+    res.sendStatus(status);
+  } catch (e) {
+    res.sendStatus(500);
+  }
+};